Portugal: double taxation agreement, Article 28: Entry into force

(1) This Convention shall be ratified and the instruments of ratification shall be exchanged at London as soon as possible.

(2) The Convention shall enter into force upon the exchange of instruments of ratification and its provisions shall have effect:

(a) In the United Kingdom:

(i) as respects income tax, surtax and capital gains tax for any year of assessment beginning on or after 6th April in the calendar year next following that in which the Convention enters into force;
(ii) as respects corporation tax for any financial year beginning on or after 1st April in the calendar year next following that in which the Convention enters into force.

(b) In Portugal: as respects Portuguese tax on profits, income or capital gains arising on or after 1st January in the calendar year next following that in which the Convention enters into force.